A nacelle generally has a tubular structure comprising an air intake upstream of the turbojet engine, a median section intended to surround a fan of the turbojet engine, a downstream section housing thrust reverser means, and intended to surround the combustion chamber of the turbojet engine, and generally ends with an jet nozzle whereof the outlet is situated downstream of the turbojet engine.
Modern nacelles are intended to house a dual-flow turbojet engine capable of generating, via the blades of the rotary fan, a hot air flow (also called primary flow) coming from the combustion chamber of the turbojet engine, and a cold air flow (secondary flow) that flows outside the turbojet engine through a jet formed between a fairing of the turbojet engine and an inner wall of the nacelle. The two air flows are ejected from the turbojet engine through the rear of the nacelle.
The role of a thrust reverser is, during landing of an airplane, to improve the braking capacity thereof by redirecting at least part of the thrust generated by the turbojet engine towards the front. In this phase, the reverser obstructs the jet of the cold flow and orients it towards the front of the nacelle, thereby generating a counter-thrust that is added to the braking of the wheels of the airplane.
The means implemented to perform this reorientation of the cold flow vary depending on the type of reverser.
Thus, grid reversers are known, as illustrated in FIGS. 1 to 3, in which the reorientation of the air flow is done by cascade vanes 1 associated with a sliding cowling 2 aiming to uncover or cover these vanes 1, the translation of said cowling 2 occurring along a longitudinal axis substantially parallel to the axis of the nacelle.
This sliding cowling 2 is thus capable of going alternatingly from a closing position illustrated in FIG. 1, in which it ensures the aerodynamic continuity of the nacelle and covers the cascade vanes 1, to an open position, in which it opens a passage in the nacelle intended for the cascaded flow and uncovers the cascade vanes 1.
Moreover, aside from its thrust reverser function, the sliding cowling belongs to the rear section and has a downstream side forming the jet nozzle 3 aiming to channel the ejection of the air flows.
This nozzle 3 comprises at least one panel 4 mounted mobile in rotation, said panel 4 being adapted to pivot between a normal position illustrated in FIG. 1, in which it ensures the aerodynamic continuity of the nacelle, a thrust reverser position in which it obstructs the cold flow jet 5 and a position illustrated in FIG. 2, causing a variation of the section of the nozzle 3.
It is possible to adjust the pivot degree of the mobile panel 4 and make it possible either to vary the jet nozzle section 3 or to cause the reversal of the cold air flow in the jet 5 in a reverse jet depending on the degree of displacement of the mobile cowling 2.
Thus, as illustrated in FIG. 2, to reduce the jet nozzle section 3 by driving the panel 4 towards the inside of the jet 5, the mobile cowling 2 must be advanced in the upstream direction towards the upstream fixed structure 6 of the nacelle.
In order to be able to ensure this simple translational movement of the mobile cowling 2 in the upstream direction and, as a result, the free movement between the mobile cowling 2 and the upstream fixed structure 6 of the nacelle, a cavity 7 is created at the interface between these two elements.
However, as illustrated in detail in FIG. 3, the presence of this cavity 7 creates a discontinuity of the aerodynamic lines of the surface of the nacelle causing a degradation of the performance of the propulsion assembly of the latter and an increase in the aircraft's consumption.